The other day I got an attack of hiccups. My grandmother’s cure was to blow into a paper bag. She didn’t know anything about neurological reflexes or phrenic and vagus nerves, which carry the hiccup messages, but her old folk remedy seemed to work. It probably did so by taking advantage of the body’s response to abnormal levels of carbon dioxide in the lungs and the blood stream. After a few breaths, the air in the bag has a much higher carbon dioxide concentration than normal. In response, our respiratory sensors in the brain call for stronger and deeper breaths. This regularizes the contractions of the diaphragm and often eliminates the spasm.
Hiccups have no known physiological function. They are a normal and frequent event in the underwater life of the fetus. Hiccups often continue to afflict newborn babies for quite a while after birth. For adults, they may well be just an annoying vestige left over from our life in the womb.
The many folk cures for hiccups, like swallowing without breathing, or being subject to a fright, probably work for the same reason the paper bag works. They raise the level of carbon dioxide in the blood stream. In extreme intractable cases, drugs may help and as a last resort even surgical crushing of the phrenic nerve has been tried.
So next time you get hiccups, remember that sometimes things happen in the body that have no known purpose.